Catalytic conversion



May 22, 1945- J. D. UPHAM ETAL 2,376,564

CATALYTIC CONVERSION- Filed Jan. 1, 1944 PRODUCTS 2a COOL HEATHRRIER 58f HEAT cARRlER DIES BODIES nc i 40/ 3B 5 D l2 E LLI lL' I I /la o I I nl; v) o o o?, m j u. u. m m

Z4: O O [[0 U01 MU i'* mo Lu n.0 3.0 g g 2m a: n u l m 'm IO/ I u l -1 dmg 8 g I2 g EL) I4 u1 4 36 (I 32 /3 L* I8 atented l22 1945 cA'rALYTIcCONVERSION John D. Upham and I.- Louis Wolk, Bartlesville,

kla.,\5 assignors to Phillips Petroleum Company, a corporation ciDelaware Application January l, 1944, Serial No. 516,614 Claims. (Cl.MiG-52) The present invention relates to conversion processes andapparatus therefor wherein a mobile catalyst is utilized. It isparticularly applicable to the conversion of hydrocarbons using apowdered catalyst suspended in hydrocarbon vapors. The invention will bedescribed with particular reference to catalytic cracking of gas oil orthe like, but it is also applicable to other conversion reactions, suchas hydroforming. dehydrogenation, cyclization, etc., especiallyendothermic conversions in which the catalyst is regenerated by theexothermic combustion of carbonaceous matter deposited thereon.

Inasmuch as cracking, dehydrogenation, etc., are endothermic reactions,the temperature of the hydrocarbon stream passing through a reactionzone generally decreases in the direction of flow, with consequentdecrease in rate of reaction. In the catalyst regeneration step, thereverse occurs, that is the temperature of the regeneration gasincreases in the direction of flow through the regeneration zone, withconsequent overheating. Our invention serves to minimize these effects,with consequent improvement in efficiency.

The use of nely divided solid catalystwhich is caused to flow through aconversion system has recently come into commercial use in the crackingor other treatment of hydrocarbon materials. In the so-called fluidcracking process, powdered solid cracking catalyst is suspended inhydrocarbon vapors in a cracking zone, withdrawn to a regeneration zonewherein carbon is burned oil' by suspension of the spent catalyst in hotoxygen-containing gases, and the regenerated catalyst then returned tothe reaction zone for further use. In such processes, the catalyst isdepended upon to a certain extent to act as heat carrier by transferringheat from the exothermic regeneration reaction to the endothermiccracking reaction which is generally carried out at a lower temperature.In order to effect transfer of a high percentage of the heat ofregeneration to the conversion zone, a fairly high ratio of catalyst toregeneration gas and reactants is used, the amount of catalystcirculated frequently being in excess of that required for the solepurpose of' catalyzing the conversion. Furthermore, the catalyst isliable to be subjected to undesirablyhigh temperatures in theregeneration zone. the excessive number of regenerations which thecatalyst undergoes for a given amount of conversion, and the hightemperature to which itliis repeatedly subjected, serve to shorten theultimate lite of the catalyst, and force its discard use after producingless product than would be the case under less severe operations.

An object of this invention is to provide improved methods and apparatusfor carrying out catalyzed reactions. A further object is to provide forthe utilization of heat generated in an exothermic reaction to supplyheat to an endothermic reaction, utilizing direct heat exchange. Anotherobject is to compensate for the tempera.- ture drop which normallyoccurs in an endothermic reaction zone. Another object is to effectendothermic hydrocarobn conversions in the presence of a mobile powderedcatalyst,V and to regenerate said. catalyst by oxidationvof carbonthereon, the while eiecting transfer ofheat from the regeneration to theconversion. A further object is to crack hydrocarbons by means of asocalled fluid catalyst while circulating a smaller amount of suchcatalyst than is normally used, and yet retaining advantages of thehuid-type catalyst. Still another object is to provide a means for atleast partially stabilizing temperatures in the conversion andregeneration zones while eiectively conserving heat. Other objects andadvantages of the invention will be apparent ii'om the accompanyingdisclosure and descrip- Brieily, our invention accomplishes its objectsby means of direct heat exchange n a novel and efficient manner,utilizing as a preferred embodiment mobile heat adsorptive andconductive bodies passed through the system in such a manner as toabsorb heat and stabilize temperatures in a regeneration zone and togive up heat and likewise stabilize temperatures in a conversion zone,said bodies being in direct contact with gases carrying the powderedcatalyst suspended therein. We preferably utilize heat retainingmaterials having better thermal properties than the catalyst, dueparticularly to higher thermal conductivity, as well' as suitably highlspeciic heat and/or density, the net eiect being to provide better heatretaining and heat transfer properties than the catalyst used. Suchmaterials are exemplifled by silicon carbide (Carborundum), iron,aluminum, copper, steel, quartz, other forms of dense silica, fusedaluminas of various types such as alundum, magnesite, etc. The heatretaining bodies are preferably inert under the conditions of use, andare preferably of a non-adsorptive nature. Y

In the preferred practice of this invention, finely divided solidcatalyst is suspended in reactant vapors and conducted through areaction zone at as too-permanently spent for further economicconversion temperatures and pressures. In the reaction zone, thesuspension of Acatalyst in reactants is contacted with mobileheatretainingv and conducting bodies. These/bodies have absorbed asubstantial amount of heat from-the regeneration zone and are at atempension of catalyst in reactant vapors is passed upwardlycounter-current to downwardly flowing heat retaining bodies ofsubstantially larger rated from products of reaction and then, with orwithout intermediate purging as required, is suspended in anoxygen-containing gas in/the regeneration zone at temperaturessuillciently high to eii'ect combustion of the carbonaceous 16 matter onsaid catalyst. Heat retentive material removed from the reaction zone ispassed through the regeneration zone for the purpose of absorbingexothermic heat of combustion, preferably by counter-current ilow to thesuspension of zo catalyst in the regeneration gases. The heat soabsorbed is transferred to the reaction zone by flow of the heatabsorbant bodies from the regeneration zone to the reaction zone asdescribed.

I2 the regeneration zone the heat retaining mag5 temperature drop isavoided in the conversion zone where the reaction in endothermic, sincethe heat retaining material supplies heat to the reaction. Onlysuilicient catalyst need be circulated to effect the desired extent ofconversion.

The catalyst may be any suitable material for the particular reactionwhich can be utilized in finely divided form, say. oi' 200-400'mesh oreven finer. Such catalysts as synthetic silica-alumina, bauxite,acid-treated clays such' as "Super Filtrolf and the like are especiallysuited to catalytic cracking operations and may be readily utilized.Other catalysts suitable for cracking or other conversion reactions arewell known to the art and need not be enumerated here.

The accompanying drawing shows somewhat diagrammatically, partly inelevation and partly in cut-away view, one advantageous arrangement ofapparatus and ow oi' materials therethrough by which the principles ofthe invention may be applied to the catalytic cracking of gas oil. It

will be appreciated that in view of the schematic nature of the drawing.numerousauxiliary items of equipment such as valves, pumps, compressors,heaters, fractionators, control equipment, etc.,

have been omitted. Such elements may be readily supplied by one skilledin the art and hence are not shown in order to avoid encumbrance of thedrawing.

In the drawing, chambers I0 and I2 are provided, the former being forreaction and the latter for regeneration. While these chambers are shownof equal size, they may, of course, differ depending upon, theparticular reaction being catalyzed, the extent of carbon deposition onthe catalyst, etc. Charge oil vapors are intro- 05 duced to the sytemvia line I4, and after picking up regenerated catalyst from standpipe I6in injector or other means i8, are passed via line 20 into a low pointof reactor I0. Additional reactants may be introduced through line 22ii' de- 70 sired. The suspension of powdered catalyst in reactant vaporspasses upwardly through reaction chamber l0 wherein the gas oil iscracked to the desired extent and thence out via line 24 to cycloneseparator 26 or the like. It is to be 75 rature above 5 Y the conversiontemperature.' Pref rably the susdownward progress.

understood that a plurality-of separators may f be'used as and ifrequired. yIn separator 26 the spent catalyst is separated from .theproducts. which are passed via line 28 to conventional fractionationmeans for recovery of products and of recycle streams.l The separatedcatalyst passes into catalyst standpipe 30 wherein it may be purgedand/or maintained in an aerated condition by conventional means notshown. particle size than thetatalyst. Catalyst is sepa- 10 Air or otheroxygen-containing regeneration gas enters the system through line 32 andpicks vup spent catalyst in unit 34. The resulting suspension passes vialine JI into regeneration chamber l2 at a low point therein. Thesuspension of spent catalyst in the oxygen-containing gases flowsupwardly through chamber I2 wherein regeneration is effected bycombustion of carbon on the catalyst. A suspension leaves the top ofregenerator l2 through line 38 and passes to one or more cycloneseparators 40 or the equivalent for separation of catalyst from gases.The

spent regeneration gases exit via line 42, while ture and thus imparts'its lheat to the reaction' mixture by direct heat exchange. 'I'heheatcarriermay have been heated in any desired manner, but in theembodi/ment illustrated in the drawing it has absorbed heat ofregeneration in chamber I2. The pellets or the like are of particle sizesubstantially greater thanthat of the powdered catalyst, so that they cwdownwardly through the chamber. This effects a countercurrent flow ofheat carrier and reaction mixture, thus providing maximum heat at theoutlet of the reaction zone where it is most needed. and a steadilydecreasing amount of heat as it progresses toward the bottom of thereaction zone where the endothermic cracking is just started. The heatcarrier particles may be of any suitable size to give the desiredresult, and will ordinarily fall within the range of from about 50 meshup to say 1 inch in diameter.

Ordinarily, particles having a diameter from about 0.1 to 0.3 inch arequite satisfactory. Chambers lo and l2 may be provided with bailies 46,preferably perforated, to aid in contacting of heat retainer with thesuspension of powdered catalyst in up-ilowing gases and to provide alonger time of residence of the heat retainer and a more even rate offlow thereof by slowing its Perforations in the banles allow arelatively free upward flow therethrough and avoid any possibility ofdead-space pockets in the chambers. 0f course, other arrangements may beused to give similar results.

When the heat carrier granules drop below the point of inlet of powderedcatalyst they may be effectively purged of any small amounts of powderedcatalyst which may have become deposited thereon by a blast from line 22of catalyst-free incoming charge vapors. However, although preferred, itis not absolutely required that all catalyst powder be thus removed.since the heat car-'- rier next passes to the regeneration zone and anyauch residual powder is retained within the system. Line 2! maydesirably be used for the introduction of steam or other inert purge gasto prevent the removal of any hydrocarbons with the heat carrier as wellas to separate residual catalyst therefrom.

Heat carrier particles which have given up heatA in passage through thereaction zone I are removed from the :bottom thereof through line 48 andpassed to elevator means 50, which desirably involves the use of amoving endless bucketcarrying chain. This equipment may be similar tothat used currently in the so-called TCC system for carrying catalystparticles from one moving bed to another. The heat carrier is dischargedfrom the top of elevator 50 and passes through line 52 to the top ofregeneration zone It. In this zone the heat carrier material is contacted with the suspension of powdered catalyst in regeneration gases ina manner similar to that Just described for chamber l0. The carrier,cooled by its contact in chamber l0, now absorbs heat of regeneration inchamber l2, thus storing it up for use in chamber I0. and effectivelycontrolling the highly exothermic regeneration by preventing localizedhot spots and excessive temperature rises. If desired, the ow ofheatretainer may be concurrent with the regeneration mixture in chamberl2, rather than countercurrent as shown. The choice will depend largelyupon the regeneration conditions, and it is preferred that the retainerleave the chamber at the end at which the highest temperature prevails.Additional regeneration gases, or purge gases. may be introduced throughline 54 for contact with hot heat carrier before the latter exits fromthe bottom of chamber I2 via line 56 for the purpose of purging the heatcarrier of residual gases and catalyst particles. Elevator I8 isutilized for carrying the hot particles to line 44 for admission to thetop of reactor l0.

Various hydrocarbon feed stocks, such as naphthas, gas oils, and thelike, may be cracked in accordance with the procedure described above.In general, cracking temperature in the range of 8501150 F. may be usedand a catalyst to oil ratio of from about 0.2 to 10 parts Iby Weight ofcatalyst per weight of oil feed is satisfactory. Ordinarily, due to theuse of the heat retaining bodies, a ratio of higher than 3 to 1 isseldom required and a ratio of l to 1 or less is frequentlysatisfactory. A contact time of 5 to 50 seconds in the conversion zoneis usually suitable, depending on the temperature of operation, natureof catalyst, etc. The amount of regeneration gas used will depend to alarge extent on the amount of carbon deposition occurring in thereaction zone. The oxygen content of the regeneration gas may range fromabout one per cent on up to that of air, and normally will be well inexcess of that required for complete combustion of carbon on thecatalyst being regenerated. Temperatures ranging from 1050 to 1250 F.are ordinarily attained in the regeneration zone.

It will be seen that the use of mobile heat retaining bodies inaccordance with our invention makes possible a. much more rapidregeneration than would otherwise be possible, since the bodies absorb asubstantial amount of the heat of reaction; the very careful anddiilcult control of regeneration conditions characteristic of presentmethods is not so critical when operating thus, due to the stabilizingeffect of the heat retaining bodies. The same types of advantagesgenerally are found in the reaction zone, since by giving up asubstantial portion of the heat required for cracking or otherconversion the heat absorbent bodies minimize the normal drop oftemperature in the reaction zone and thus greatly increase the rate ofreaction. Furthermore, the countercurrent ilow of heat Icarrier andreactants allows a much more uniform temperature to prevail thruout thereaction zone.

It will be understood that various conventional operations and/orequipment may be supplied by one skilled in the art as required withoutdeparting from the invention. Furthermore, although the invention hasbeen described specincally with reference to the endothermic conversionsof hydrocarbons, the principles thereof may readily be applied withsuitable modiiications to other conversions or chemical reactions.

We claim:

1. In the conversion of hydrocarbons wherein finely divided solidcatalyst is passed through a circuit comprising a reaction zone whereinsaid catalyst is suspended in gaseous reactants for effecting saidconversion and in a reactivation zone wherein said cataLvst is suspendedin hot oxygen-containing gases for burning carbonaceous material fromsaid catalyst, the improvement which comprises introducing saidsuspended catalyst and a relatively inert mobile solid heat absorbentmaterial oi. superior thermal properties and larger particle size thansaid catalyst into opposite ends of said conversion zone, withdrawingabsorbent material and catalyst from ends of said conversion zoneopposite their points of introduction, separating said catalyst from theeilluent, separately introducing said catalyst and absorbent materialinto opposite ends of said regeneration zone, withdrawing heatedabsorbent material and regenerated catalyst from ends of regenerationzone opposite their points of introduction, and recycling each to saidconversion zone. x

2. In the endothermio catalytic cracking of hydrocarbons in whichcracking catalyst having a particle size substantially within the rangeof about 200 to 400 mesh is contacted with hydrocarbon vapor in areaction zone and then with oxygen-containing gases in an exothermicregeneration zone at a higher temperature, the method of transferringheat from the regeneration zone to the reaction zone which comprisesowing downwardly in said Vregeneration zone through up-flowingregeneration gases and suspended catalyst being regenerated at atemperature of about 1050-1250 F. a heat absorbent solid having a higherheat capacity than said catalyst and having a particle sizesubstantially within the range of about 0.1 to 0.3 inch in diameterwhereby a portion of liberated heat is absorbed thereby, separatingregenerated catalyst from regenerating gases and recovering hot heatabsorbent naterial from the bottom of the regeneration zone, suspendingsaid regenerated catalyst in the hydrocarbon vapors, and passing theresulting suspension through said reaction zone at a temperature ofabout 850-1150 F. in countercurrent contact with down-flowing heatedabsorbent material removed from the bottom of said regeneration zone.

3. The process of claim 2 in which said catalyst is separated from theellluent from reaction zone and is suspended in up-ilowingoxygen-containing regenerating gases in said regeneration zone incounter-current contact with heat absorbent material removed from bottomof said reaction none for downward iiow in the regeneration zone asdescribed.

4. The process of claim 2 in which the heat absorbent particles arepurged oi residual catalyst and gases prior to passage to another zone.

5. In the endothermic conversion oi' hydrocarbons wherein finely dividedsolid catalyst is passed through a circuit comprising a reaction zonewherein said catalyst is suspended in gaseous reactants for effectingsaid conversion and wherein a temperature drop normally tends to occurin the direction of now of reactants due to the endothermic nature ofthe reaction, and a reactivation zone wherein said catalyst is suspendedin hot oxygen-containing regeneration gases for the combustion ofcarbonaceous deposits thereon and wherein a rise in temperature tends tooccur in the direction o! flow of regeneration gases due to theexothermic nature of the reaction. the method for compensating for saidendothermic temperature drop and said exothermic temperature rise,respectively.. which comprises introducing relatively cool particles ofa heat retaining material having a higher heat capacity than saidcatalyst into the reactivation zoneandiiowingsamecountercurrenttotheiiow oi.' said catalyst suspended in the regenerationgases whereby a substantial proportion of the liberated heat will beabsorbed by said heat retaining material, separating said regeneratedcatalyst and the hot heat retaining material at 0p posite ends of saidreactivation zone, suspending said regenerated catalyst in reactants andilowing said suspension through said reaction zone, introducing said hotheat retaining material into the reaction zone at the opposite endthereof and ilowing same countercurrent to said catalyst sus pensionwhereby a substantial proportion oi the heat absorbedin said heatretaining material will be imparted to the reaction zone in the regionwhere the greatest temperature drop occurs, recovering the thus-cooledheat retaining material and the spent catalyst from opposite ends of thereaction zone, and returning said catalyst and said heat retainingmaterial to said reactivation zone.

JOHN D. UPHAM. I. LOUIS WOLK.

